64 OBSTETRICS. 



sound, which appears to proceed from the liquor amnii, and to be 

 partly produced by the movement of the child, which seems to an- 

 ticipate the coming on of the contraction ; nearly at the same 

 moment all the tones of the uterine pulsations become stronger ; 

 other tones which have not been heard before, and which are of a 

 piping, resonant character, now become audible, and seem to vibrate 

 through the stethoscope, like the sound of a string which has been 

 struck and drawn tighter, while in the act of vibrating."* As the 

 pain grows stronger, the pitch rises. By the time the pain has 

 reached its height, the sound has entirely ceased, or become very 

 faint ; as it departs, however, the sound again returns as at the 

 beginning of the pain, and finally resumes its former tone, which it 

 had during pregnancy. The noise made by the escape of the blood 

 through the uterine veins during a contraction, is probably an im- 

 portant element in the production of the sound in question. 



It is remarked also by the author quoted above, that the pulse 

 increases in rapidity in proportion as the pain rises in intensity, 

 subsiding in the same manner with it. As the labour advances, the 

 rapidity of the pulse increases, so that shortly before the child is 

 born, it has attained the maximum that it had during the height of 

 the pains in the commencement. 



A per vaginam examination at the commencement of labour re- 

 veals to us the condition of the parts through which the child is 

 about to pass. If the vagina is cool, moist, and cushiony, and the 

 OS uteri soft and thick, the dilatation will most probably proceed 

 favourably. If, on the contrary, the vagina is hot and dry, and the 

 OS uteri hard and thin, or hard and thick, the first stage will generally 

 be tedious. T'he time occupied in the first stage varies very much 

 in different women, and in the same women in different labours. 

 In primiparse, it is generally longer than in those who have had 

 several children. Regular and genuine contractions seldom require 

 more than six hours to perfect this stage, and often it is accomplished 

 in much less. The dilatation also proceeds much more slowly at 

 the commencement, than it does later ; this is owing to the want of 

 the mechanical dilatation which it afterwards receives by the forma- 

 tion of the bag of waters, which acts as a wedge, and forcibly dis- 

 tends the OS uteri. 



Bag of waters. — As the circle of the os uteri enlarges, the mem- 

 branes of the ovum, containing a portion of the liquor amnii, pro- 

 trude through the opening, forming a tense, elastic, conical bag ; 

 this by its mechanical pressure assists in the dilatation of the os 

 uteri. During a pain it can be felt becoming more and more tense, 

 and again relaxing as the pain subsides, so that the presenting part 

 can often be detected through it. 



Near the end of the first stage streaks of blood will often be 



* Rigby, p. 159. 



